The invention relates to a magnetic-inductive flow meter with clocked excitation.
Inductive flow meters described in the U.S. Pat. Nos. 5,018,391 and 5,400,660, both granted to Doll, or in U.S. Pat. No. 3,783,686 operate in the form of clocked alternating field devices generating a magnetic field in the flowing liquid by supplying exciting pulses derived from the primary frequency to a coil. The clock frequency of the exciting pulses of the coil is about 1/3 to 1/10 of the primary frequency. The exciting current pulses generate pulses of magnetic field strength in the flowing medium. At electrodes which are in contact with the medium, an electric potential is generated whose magnitude is proportional to the field strength and the flow velocity. Thus, a measuring signal is obtained which is a measure of the flow velocity of the flowing medium. The reaction time of the flow meter depends on the clock frequency by which the coil is excited. Further, it has to be considered that numerous noise components occur, falsifying the measuring signal and impairing the measuring accuracy and stability of the flow signal.